(1) Field of the Invention
This invention relates to the control of flowing molten metal passing, for example, through molten metal troughs, runners, channels, or the like. More particularly, the invention relates to movable flow control elements.
(2) Description of the Related Art
Molten metals used in industry are often transferred from one location to another through an open trough, runner or channel (referred to simply as a “trough” in the following description), or they may be transferred directly from one furnace to another. During such transfer, it is often necessary to interrupt, divert or slow the flow of molten metal. For example, aluminum or aluminum alloys may be melted in a metal melting furnace and transferred through a series of troughs to casting apparatus for producing cast ingots or other products, and a molten metal dam is sometimes arranged within the trough so that the metal flow can be shut off, or so that a section of the trough can be drained for inspection or repair, or so that the section of trough can be replaced or the trough extended. At other times, it may be necessary to isolate a body of molten metal in a channel or section of a trough, but to allow a small amount of metal to escape in order to maintain a desired temperature in the main body of metal. Such an arrangement is referred to as a bottom bleed system and amounts to a dam that terminates a small distance above the bottom of a trough or channel. Devices of this kind, and others, may be referred to generally as movable flow control elements and they may include molten metal gates, dams, shutters, plugs, stoppers, and the like.
Movable flow control elements of this kind, when used with a trough, are typically mounted on a fixed frame or gantry that straddles the trough. An actuating device, e.g. a motor, for moving the element into or out of the trough is mounted on a horizontal cross-member of the frame and is provided with controls so that the element can be moved up or down when, and to the extent, required, e.g. to start or stop the metal flow. The element itself is generally made of a rigid refractory material, e.g. metal or ceramic, having a shape similar to that of the cross-section of the trough and may be provided with a layer or bead of compressible material around its edges to create a seal to prevent metal penetration when the element is in the closed position. There are, however, several problems with this kind of arrangement. For example, because the frame straddles the trough, and usually has a cross-member linking both sides, it causes difficulties of access to the trough interior when cleaning or maintenance is required. Furthermore, the actuating device is exposed to heat and vapors from the metal trough, which may shorten its active life, and may cause danger or discomfort for workers carrying out maintenance or repairs on the device. Additionally, the extent by which the element may be removed from the trough is often limited, so that access to it for maintenance or repair is difficult. There is therefore a need for an improved arrangement to overcome or at least to minimize some or all of such difficulties.
U.S. Pat. No. 5,162,093 which issued on Nov. 10, 1992 to Fournier et al. discloses a device for opening and closing a vessel containing molten metal. In this case, the device includes a conical stopper that forms a removable plug in a drain hole provided in a sidewall of a metal holding vessel, e.g. a furnace or ladle, at or near the bottom of the vessel. The plug is attached to a pair of rotatable arms mounted on the side wall that allow the stopper to be moved into and out of the drain hole as required. The arms are pivotably attached to the plug and to the side wall to guide the plug in fixed path such that it initially moves approximately axially of the drain hole, and then later moves in a curved path away from the drain axis. This motion is reversed when the plug is returned to the bore to stop the metal flow.
U.S. Pat. No. 4,390,169 which issued to Michael D. LaBate on Jun. 28, 1983 discloses a gate positioned within a metal runner. The gate is attached to a lifting device that allows the gate to be raised or lowered. The lifting device includes an arm pivotally attached to an upright post at one side of the runner and having a suspended weight at the other side of the trough. The gate is raised or lowered manually a handle or via a rope.
U.S. Pat. No. 2,348,521 which issued to Carter et al. on May 9, 1944 also discloses a gate for a molten metal runner. The gate is attached to a centrally pivoted arm that extends beyond one side of the runner and is provided with a weight at the far end. The weight is located within a housing and is held in an upper position by a latch when the gate is in the closed position. When the latch is released, the weight falls freely in the housing for a time to take up slack, and then lifts the gate with a jerking action as the slack plays out.
U.S. Pat. No. 608,143 which issued to Michael Killeen on Jul. 26, 1898 discloses a skimmer movably positioned within a molten metal skimmer trough. The skimmer is attached to a lever that is pivoted in the center and extends to one side of the trough. The skimmer may be manually raised or lowered simply lowering or raising the free end of the lever.